The analysed samples treated with ultrasound for 20 or 30 min exhibited better colour retention in the dried state as compared to the untreated or pre-treated samples for a shorter time, i.e. for 10 min.
The analysed samples treated with ultrasound for 20 or 30 min exhibited bettercolour retention in the dried state as compared to the untreated orpre-treated samples for a shorter time, i.e. for 10 min.